3,197 research outputs found
Observation of Entanglement-Dependent Two-Particle Holonomic Phase
Holonomic phases---geometric and topological---have long been an intriguing
aspect of physics. They are ubiquitous, ranging from observations in particle
physics to applications in fault tolerant quantum computing. However, their
exploration in particles sharing genuine quantum correlations lack in
observations. Here we experimentally demonstrate the holonomic phase of two
entangled-photons evolving locally, which nevertheless gives rise to an
entanglement-dependent phase. We observe its transition from geometric to
topological as the entanglement between the particles is tuned from zero to
maximal, and find this phase to behave more resilient to evolution changes with
increasing entanglement. Furthermore, we theoretically show that holonomic
phases can directly quantify the amount of quantum correlations between the two
particles. Our results open up a new avenue for observations of holonomic
phenomena in multi-particle entangled quantum systems.Comment: 8 pages, 6 figure
Multipartite entanglement in fermionic systems via a geometric measure
We study multipartite entanglement in a system consisting of
indistinguishable fermions. Specifically, we have proposed a geometric
entanglement measure for N spin-1/2 fermions distributed over 2L modes (single
particle states). The measure is defined on the 2L qubit space isomorphic to
the Fock space for 2L single particle states. This entanglement measure is
defined for a given partition of 2L modes containing m >= 2 subsets. Thus this
measure applies to m <= 2L partite fermionic system where L is any finite
number, giving the number of sites. The Hilbert spaces associated with these
subsets may have different dimensions. Further, we have defined the local
quantum operations with respect to a given partition of modes. This definition
is generic and unifies different ways of dividing a fermionic system into
subsystems. We have shown, using a representative case, that the geometric
measure is invariant under local unitaries corresponding to a given partition.
We explicitly demonstrate the use of the measure to calculate multipartite
entanglement in some correlated electron systems. To the best of our knowledge,
there is no usable entanglement measure of m > 3 partite fermionic systems in
the literature, so that this is the first measure of multipartite entanglement
for fermionic systems going beyond the bipartite and tripartite cases.Comment: 25 pages, 8 figure
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